The invention relates to display screens and display screen construction, and more particularly to devices and methods for lacquering the inner side of a display screen.
Such a device and method have been used by the applicant for many years and are therefore known. In the known device and in the known method, the sealing means are provided with a frame-shaped flat rubber piece connected to the closing means by way of a connection frame, which flat rubber piece constitutes a sealing lip extending towards the frame-shaped peripheral area of a display screen inserted into the known device, the sealing lip substantially comprising four sealing lip sections and engaging the outer peripheral boundary face of the peripheral area of this display screen. In the known device and method, it is necessary to ensure a preferably exact positioning of the rubber ring and its sealing lip, for which appropriate adjusting measures are required. A further aspect is to be taken into account during permanent operation of the known device because the sealing lip may be contaminated when this is not prevented by suitable cleaning measures. To resist the solvent in practically every lacquer, such as toluene, the use of a solvent-resistant viton rubber for the rubber ring and its sealing lip is essential.
It would be advantageous to provide an improved device and an improved method, in which improved sealing means are used, which prevent the above-mentioned difficulties in a simple and low-cost manner.
Accordingly, in one aspect of the invention, a method of lacquering the inner side of a display screen having a front area that extends substantially transverse to a display screen axis, and a peripheral area remote from the front area and extends substantially parallel to the display screen axis, the peripheral area being bounded by an outer peripheral boundary face, comprises: positioning the display screen at a lacquering head that encloses an inner space and is closed at the top with a closing plate that has a passage bounded by a passage boundary face and can be covered by the display screen while leaving free a spacing between the passage boundary face of the passage in the closing plate and the peripheral area of the display screen covering the passage in the closing plate, and through which passage the inner side of a display screen can be lacquered; providing the lacquering head with a support with which a display screen covering the passage in the closing plate can be axially supported, and in whose inner space lacquer-supply passage can be inserted; providing the lacquering head with a sealing structure that seals the spacing; bringing the peripheral area of the display screen is into proximity of the passage in the closing plate of the lacquering head; axially supporting the display screen in a lacquering position by the support of the lacquering head, in which position the display screen substantially covers the inner space of the lacquering head; and after the display screen has reached its lacquering position, supplying lacquer via the lacquer-supply passage to lacquer the inner side of the display screen, during which lacquering operation a gaseous medium is released in the inner space of the lacquering head, and escape of the released gaseous medium from the inner space of the lacquering head is counteracted by the sealing structure with which the lacquering head is provided. While positioning the display screen at a lacquering head, the peripheral area of the display screen is being brought into the proximity of the passage in the closing plate of the lacquering head, an air gap present between an inner frame boundary face of a frame and an outer peripheral boundary face of the peripheral area of the display screen is formed between the peripheral area of the display screen and the frame associated with the sealing structure and being bounded by the inner frame boundary face, the air gap constituting a flow resistance as a result of its dimensions and counteracting the escape of the released gaseous medium from the inner space of the lacquering head.
With the invention, an essentially simpler device is obtained in which sealing means realized in a very simple manner and yet being very effective are provided, in which with relatively little maintenance, the desired object is achieved, which is of great advantage for a high capacity utilization of a device according to the invention. The sealing means are advantageously realized without mechanical contact with the display screen present proximate to the lacquering head, which is very advantageous with a view to realizing a longer lifetime and avoiding an unwanted contamination. The air gap formed by means of the frame advantageously represents a uniformly effective flow resistance which counteracts an escape of a gaseous medium, such as toluene, from the inner space of the lacquering head in each air gap area with the same resistance, which is very advantageous for a spatial and temporally homogeneous drying of the lacquer on the inner side of the display screen.
One embodiment of the invention, described herein, yields the advantage that the display screen to be lacquered, inserted into the frame and axially supported, can be very accurately positioned transversely to the display screen axis, so that an equal width of the air gap along the entire outer peripheral boundary face of the peripheral area of the display screen is ensured.
Some embodiments of the invention may be equipped, for example, with a frame having an inner frame boundary face whose longitudinal extension extending parallel to the display screen axis is smaller than the extension, extending substantially parallel to the display screen axis, of the outer peripheral boundary face of the peripheral area of the display screen. Likewise, a device according to the invention may be equipped, for example, with a frame having an inner frame boundary face, whose longitudinal extension extending parallel to the display screen axis is larger then the extension, extending substantially parallel to the display screen axis, of the outer peripheral boundary face of the peripheral area of the display screen. In both cases, a desired flow resistance of the air gap can be achieved by a corresponding choice of its dimensions.
An embodiment of the invention described herein advantageously provides an air gap between the inner frame boundary face of the frame and the outer peripheral boundary face of the peripheral area of each display screen to be lacquered. It has further proved to be very advantageous when an end zone of the frame bounding the inner frame boundary face of the frame at its end remote from the closing means and an end zone of the display screen bounding the outer peripheral boundary face of the peripheral area of the display screen covering the passage in the closing means at its end remote from the closing means are substantially situated in a plane extending transversely to the display screen axis of the display screen. Apart from positioning, alignment and dimensioning of the inner frame boundary face of the frame, it may also be noted that the inner frame boundary face of the frame may have a completely smooth surface, but also a surface structure which is completely or partly roughened or is uneven so as to obtain a desired flow resistance.
In an embodiment of the invention described herein, to ensure mechanical stability the frame has a dimension extending transverse to its inner frame boundary face that substantially corresponds to the longitudinal extension, extending parallel to the display screen axis, of the inner frame boundary face of the frame. Furthermore, the provision of this feature has a positive influence on the flow resistance of the air gap, because turbulent air streams, which may possibly occur during rotation of the lacquering head in an area of an outer edge of the frame and may lead to air pressure differences along each outer edge of the frame, are inhibited by the side of the air gap facing the front area of the display screen.
In an embodiment of the invention described herein, the frame has a substantially rectangular cross-section. This has proved to be very advantageous because it ensures a very simple possibility of manufacturing the frame.
In an embodiment of the invention described herein, to provide easy insertion and prepositioning of each display screen, the side of the frame remote from the closing means has an inlet chamfer blending with the inner frame boundary face.
In an embodiment of the invention described herein, the side of the frame facing the closing means has an outlet chamfer blending with the inner frame boundary face. In this way a lasting contamination of the air gap with lacquer residues is avoided during lacquering of the display screen, so that the air gap remains free from contaminations and the sealing property of the air gap is maintained so that a longer and maintenance-free use of the frame in the device is possible.
In an embodiment of the invention described herein, the frame has at least one recess which is accessible from the outer side of the frame and is provided to retain the frame. This provides the possibility of a simple manual or machine-operated manipulation of a frame, when applying the frame to the lacquering head and when removing the frame from the lacquering head, as is done, for example, when a frame is replaced.
In an embodiment of the invention described herein, a quick-release connection provides the possibility of simple and rapid fixation and detachment of the frame onto and from the closing means without having to use additional auxiliary means.
In an embodiment of the invention described herein, the frame is made of a solvent-resistant material. This avoids an environmentally unfriendly and frequent waste of the frame and thus ensures an optimum environmentally friendly utilization of material resources and an economically efficient operation of the device according to the invention.